Crap, you've done it again. やってしまってね。 Or did you actually mean to do it and it's a good thing? What does shimatta mean?? As is often the case in Japanese, context is everything... Let's learn about this extremely common conjugation in Japanese in a way that makes sense so you can begin using it.
Kumiko Sensei is taking the lead today – you can see her previous article on kikoeru vs. kikeru here!
Japanese Text Example: What Does Shimatta Mean?
感情表現として使われる「しまった！」は失敗した時などに自然と口をついて出てくる言葉です。「しまった！鍵を忘れた！」のように使い、「あっ」、「やれやれ」のような意味になります。英語の「 Oops 」に似ていますね。
"It was a really important document so I immediately closed it in my bag." This shimatta (しまった) is the past tense of shimau (しまう).
"I was late." The use of shimatta here is different and shows that the speaker is declaring a sense of "completion" or otherwise "regret" about the action. Let's take a look at how it can be used.
The use of shimiatta in, "I wrapped up my practice for class by yesterday" is showing a sense of completion, so it means that the speaker completed all of their practice. In the case of the shimatta in, "I was late for class," it's more about the sense of regret or how unfortunate that was.
As for which shimatta is being used, there's context in the passage that you can usually use, but the verb should also give you a hint. "To be late," "to be afraid," are not things that you consciously try to do. These types of verbs take on a sense of regret or of being unfortunate when conjugated with shimatta.
There is also the use of shimatta as an emotional expression when you've done something wrong or were rude by accident (editor's note: similar to "damn it" but softer, depending on context). "Damn it, I forgot my key!" It can be similar in use to are or yareyare in meaning. It can also be similar to "oops" in English.
One additional version of shimatta is the chatta ending. This is more casual, and shortens the final て of the phrase to make it shorter. In this case the same phrase could be said two different ways, depending on who your audience is.
机の上に置いてあったクッキーを食べてしまった sounds a lot more regretful and less playful than 机の上に置いてあったクッキーを食べちゃった。
Shimatta is super useful to be aware of – you likely won't go a day in Japan without hearing it in some capacity.
However, it's important to note that the common use of it referring to something regretful or unfortunate doesn't mean you can't use to it say that you completed something. If you're stating it to a superior (for example, at the office), you'll definitely want to class it up a touch and use shimaimashita.
Fun fact you can use to impress your friends (or scare your partner!): the phrase can also refer to getting "knocked up" with the same connotation – できちゃった！